With a view to masking a drug or the like having an unpleasant taste and controlling its release profile, numerous technologies have been reported to date for applying coating such as film coating to the drug.
For example, there has been reported a composition, which comprises layers of a drug such as ketoprofen provided on pellets formed of microgranules of an inert material and coating films of stearic acid and ethylcellulose or paraffin and a methacrylic acid copolymer provided on the layers of the drug, and which has sustained release properties over 4 to 22 hours or longer (Patent Document 1).
There has also been reported a dry syrup characterized by comprising coated particles obtained by applying coating films of any one of (a) stearic acid and a surfactant, (b) stearic acid, a surfactant, and a gastric polymer or enteric polymer and (c) a hydrogenated oil and a gastric polymer or enteric polymer onto spherical microparticles formed of a wax-like substance in which a readily water-soluble drug having an unpleasant taste is dispersed (Patent Document 2).
A taste-masking drug preparation comprising a coated powder or coated granule has also been reported. The coated powder or coated granule is characterized in that it comprises core particles, which contain a drug having an unpleasant taste, and coating films formed of a low melting-point substance and a low molecular-weight water-soluble substance and applied on the core particles (Patent Document 3).
A powder with a drug-containing, sustained-release preparation and a sweetener-containing placebo powder mixed therein has also been reported (Patent Document 4).
In the meantime, the present applicant has also reported technologies on microparticles or the like, which are formed of a low melting-point substance or the like with a drug, which has an unpleasant taste, and a gastric high-molecular compound dispersed or dissolved therein to mask the drug and to control its release profile (Patent Documents 5 to 7).
As one of preparation forms suitable for the administration of medicines to infants, dry syrups are known. A dry syrup is administered by suspending or dissolving it in water. When an infant is reluctant to take the dry syrup, it may be added to another drink which the infant likes, and may then be administered. The above-described microparticles or the like offer no problem when they are dissolved in water or the like and are then drunk. When taken in a form dissolved in an acidic drink such as a fruit juice drink, however, the drug contained in the microparticles may be immediately released, and due to its unpleasant taste, it may conversely become unpalatable.    Patent Document 1: JP-B-2518882    Patent Document 2: JP-B-3247511    Patent Document 3: JP-A-11-349473    Patent Document 4: JP-A-2001-270821    Patent Document 5: JP-B-3265680    Patent Document 6: JP-B-2973751    Patent Document 7: JP-A-2000-169364